1. Field of the Invention
The present invention relates to a motor control apparatus for positioning an object moved by rotation of a motor at a predetermined position, a motor control method thereof, a disk apparatus incorporating the above motor control apparatus, and a disk access method.
2. Description of the Related Art
A motor is generally used as a drive source for moving an object. Such motor includes a voice coil motor (hereinafter simply referred to as a VCM), a DC motor and the like. When the object moved by these motors is positioned at a predetermined position, a feedback control system is generally employed.
In the feedback control system, an input reference movement amount is compared with an object movement amount resulting from the rotation of the motor and a phase compensation means for stabilizing the control system phase-compensates a deviation which is a compared result to supply the phase-compensated deviation to a motor, thereby the object being moved at a higher speed as a distance indicated by the reference movement amount is long. The phase compensation means includes a means for carrying out only an I operation (proportional operation), a means for carrying out a PI operation (integration+proportional operation) or the like.
One of electronic equipments each incorporating a control mechanism for positioning an object at a predetermined position as described above is an optical disk apparatus mounted with an optical pickup for optically accessing an information signal recorded on an optical disk such as a CD-ROM, a magneto-optical disk or the like, for example.
A large number of the above optical disk apparatus employing the VCM, for example, as a drive source for moving the above optical pickup to a predetermined position (track) of the optical disk have been proposed and put into practice.
One of important factors for improving a performance of a disk apparatus is an increase of a speed of an operation for moving the optical pickup to a predetermined position, i.e., a seek operation. In order to carry out the seek operation at a higher speed, various attempts have been made and consequently a drive mechanism employing a linear motor or a stepping motor with a position sensor has been mainly used to achieve the high-speed seek operation.
When the moving mechanism employing the stepping motor is used to roughly move the optical pickup to a desired position, a target number of tracks is converted into a distance (movement step number) and the mechanism moves the optical pickup based on the conversion result. The movement step number is calculated based on a distance by which the optical pickup must be moved, a track pitch and a feed screw pitch. This calculation is carried out on the assumption that the track pitch and the screw pitch respectively have their predetermined values (e.g., center values of standard ranges).
When a magneto-optical disk having a diameter of 64 mm, for example, is used as an optical disk, its track pitch is 1.6xc2x10.1 xcexcm. Even if the above movement step number is calculated on the assumption that the track pitch is 1.6 xcexcm, the actual track pitch may be different from the assumed value by 0.1 xcexcm.
Since the above magneto-optical disk has about 9600 tracks at maximum, if the assumed track pitch is different from the actual track pitch by 0.1 xcexcm, then, when the movement distance is calculated from the number of tracks obtained based on the above assumed value, the difference between the distance by which the optical pickup must be moved and the calculated movement distance reaches about 960 xcexcm. Since the difference therebetween of 960 xcexcm corresponds to a difference therebetween of about 600 tracks, it takes a considerable time to position the optical pickup to a target track by using the stepping motor, which delays an access operation.
This disadvantage is also involved by the feed screw pitch, similarly. Since there is the difference between an assumed value of the feed screw pitch and the actual feed screw pitch, the difference leads to the delay in the operation of positioning the optical pickup.
In view of such aspects, it is an object of the present invention to provide a motor control apparatus and a motor control method which, even if an assumed value of a physical attribute and an actual value thereof are different from each other, can position an object to be moved at a target position at high speed.
It is another object of the present invention to provide a disk apparatus and a disk access method which, even if an assumed value of a track pitch and an actual value thereof are different from each other, can position an head at a target position at high speed and to access data recorded on a disk at higher speed.
According to a first aspect of the present invention, a drive-means control apparatus includes a movement-amount calculating means for calculating a movement amount obtained when an object to be moved is moved relative to an object to a target position on the object on the basis of an assumed value set in consideration of a physical attribute of the object, a drive means for moving the object to be moved based on the movement amount obtained by the movement-amount calculating means, a guide means for guiding the object to be moved in a direction toward the target position, an error detecting means for detecting an error between the assumed value and an actual value of the physical attribute based on a position which the object to be moved has reached after its movement and on the target position to output an error information, and an assumed value correcting means for correcting the assumed value based on the error information.
According to a second aspect of the present invention, a drive means control method includes a movement-amount calculating step of calculating a movement amount obtained when an object to be moved is moved relative to an object to a certain target position on the object on the basis of an assumed value set in consideration of a physical attribute of the object, a drive step of moving the object to be moved based on the movement amount obtained in the movement-amount calculating step, a guide step of guiding the object to be moved in a direction toward the target position, an error detecting step of detecting an error between the assumed value and an actual value of the physical attribute based on a position which the object to be moved has reached after its movement and on the target position to output an error information, and an assumed value correcting step of correcting the assumed value based on the error information.
According to a third aspect of the present invention, a disk apparatus for accessing a disk with its head includes a rotating means for rotating a disk loaded thereonto, a head guided in the radius direction of the disk for accessing an information data on the disk, a head-movement-amount calculating means for calculating a movement amount obtained when a head is moved to a target position on the disk on the basis of an assumed value set in consideration of a physical attribute of the disk, a head moving means for moving the head based on the movement amount obtained by the head-movement-amount calculating means, a guide means for guiding the head in a direction toward the target position, an error detecting means for detecting an error between the assumed value and an actual value of the physical attribute based on a position which the head has reached after its movement and on the target position to output an error information, and an assumed value correcting means for correcting the assumed value based on the error information.
According to a fourth aspect of the present invention, a disk access method of accessing a disk with a head includes a rotating step of rotating a disk loaded thereonto, a head-movement-amount calculating step of calculating a movement amount obtained when a head is moved to a target position on said disk on the basis of an assumed value set in consideration of a physical attribute of said disk, a guide step of guiding said head in a direction toward said target position, a head moving step of moving said head based on the movement amount obtained in said head-movement-amount calculating step, an error detecting step of detecting an error between said assumed value and an actual value of said physical attribute based on a position which said head has reached after its movement and on said target position to output an error information, and an assumed value-correcting step of correcting said assumed value based on said error information.